1. Field of the Invention
The present invention relates to a method and apparatus for recycling laminated films. For instance, the laminated films may comprise a milk carton (a milk container made of paper), a retort pouch used for packaging a brick-type paper container or packaging curry sauce or stew, a laminated film which includes an aluminum foil layer and is used as wrapping paper for chocolate bars, and various types of laminated films which are composed of a plurality of different materials such as paper, aluminum foil, and plastic film. The present invention relates to a method and apparatus for individually collecting layers forming a laminated film by peeling and separating them from one another. More preferably, the present invention relates to a method and apparatus for reproducing high-quality virgin materials from pulp of the laminated film including a layer of paper (hereinafter referred to as a paper layer).
2. Description of the Prior Art
A laminated film combines the lightweight and ease-in-processing features of paper, the waterproof and heat-sealing characteristics of plastic film, and the gas barrier properties of aluminum foil. Further, the laminated film is relatively easily disposed of after it has been used. Because of these features, it is very popular to package articles in a laminated film which is made using laminating or coating techniques. One type of package particularly widely used is a paper container with a laminated film (hereinafter simply referred to as a paper container) which is made of a paperboard sandwiched between layers of plastic film, as shown in FIG. 7. The paper container of this type is used for containing milk, etc. Another paper container with a laminated film is made of a paperboard having both ends covered with aluminum foil and plastic films further laminated on the aluminum foil. This type of paper container is used for containing long-life milk, fruit juice, and so forth. Even when counting only milk packages, nine million packages or more are produced every day throughout Japan.
The above-mentioned packaging containers have normally been discarded together with flammable wastes before incineration. As described above, laminated films include layers made of various materials, and hence simple incineration of the laminated films may generate noxious fumes or environmental pollution. If the waste laminated films could be recycled, it would be possible to contribute to the preservation of the environment as well as to the conservation of natural resources which tend to become depleted.
However, it is difficult to recycle the above-described laminated films comprising a plurality of different material layers. Although the laminated films including paper layers have so far been recycled, the laminated films comprising many different material layers are never recycled yet. In the meantime, laminated films comprising paper layers are recycled in the same manner as waste paper is recycled in a manner described below, and therefore, various problems are encountered in the recycling of such laminated films.
As an initial step, the laminated films which include paper layers are introduced together with water and chemicals into a bath having mixing vanes. Paper included in the laminated films is disaggregated in water and fibrously disentangled. Foreign substances are eliminated from a suspension in which the fibrous paper is mixedly included. To more completely disaggregate the paper, the suspension is introduced into a high-speed disaggregating machine. The thus disaggregated suspension passes through a mesh filter, so that plastic film and aluminum foil are removed from the suspension. Subsequently, sodium hydroxide, which acts as a deinking agent; alkaline chemicals; and a detergent are mixed into the suspension in which the laminated film is disaggregated. Shredded plastic sheets, aluminum foil, and small foreign particles such as hair are again eliminated, and the suspension is then dehydrated. The resultant pulp is fed to a bleaching process, whereby bleached pulp is recovered.
In the above described conventional method of recycling the laminated films comprising paper layers, the films are mixed in a liquid substance in order to fibrously disentangle the paper in the laminated films. Printed layers come away from the surface of the laminated films and are dispersed in the suspension. As a result, the thus-recovered paper fibers are colored by the dispersed ink.
It is difficult to completely recover the fibrous paper layers from the suspension while leaving other substances behind. Unrecovered fibrous paper, shredded plastic films, and aluminum foil remain mixed in a waste liquid from which the paper fibers have been recovered. It is necessary to recover these mixed substances by precipitating them in a settling bath before disposing of the waste liquid.
Further, it is necessary to neutralize the chemicals introduced in the waste liquid when disposing of the waste liquid in which various chemicals are mixed. Various costs incurred by the steps and equipment required to carry out the neutralizing operation are considerably large.
According to the above described conventional recycling method, it is possible to recover paper layers from the laminated films comprising the paper layers, but it is impossible to individually recover the plastic film layer and the aluminum foil layer in a recyclable manner.